1. Field of the Invention
The present invention refers to a manually operated dispensing device for cartridges, comprising a friction brake acting upon a thrust rod, said friction brake having a brake spring which frictionally acts upon the thrust rod. The latter comprises a toothing coacting with a corresponding toothing of a drive member.
The first and major task of friction brakes is to allow a relief stroke of the thrust rod after each advance stroke, said relief stroke being dictated by the relief of the flexible cartridges. That is, the friction brake should not substantially hinder the thrust rod but efficiently neutralize the trailing force being created by the drive member during grip regain and acting upon the thrust rod. Whereas the thrust rod, or the thrust rods in the case of a two-component cartridge, is guided during the advance motion by being in meshing engagement with the drive member, there is a risk during grip regain that the thrust rod is pushed somewhat offset, and the precise meshing with the teeth of the drive members is no longer guaranteed.
2. Description of the Prior Art
A dispensing device such as mentioned above has already become known from U.S. Pat. No. 4,826,053 to the same Applicant. The friction brake which has been disclosed in that document is composed of many single parts which occupy a rather great space and do not allow an alignment.
The document EP-A-0,791,404, to the same Applicant too, discloses a simplified friction brake which consists of an omega shaped spring only. It has turned out, however, that such an omega shaped spring is difficult to be adjusted to the dimensions of the thrust rod and, moreover, does not align the thrust rod.